This invention relates in particular to measuring systems. Examples of such measuring systems which are designed as coordinate-measuring devices can be found, for example in WO 2005/017448, EP 2 270 425 or WO 2006/079604. These measuring systems have a plurality of subsystems, especially in the form of electronic linear and/or rotary encoders for measurement value acquisition, which are in a communication relationship with a controller for measurement value evaluation and control of the measurement processes. These subsystems are mainly disposed on the machine in a spatially distributed manner, so that the establishment of the communication connection between the subsystems participating in the communication incurs a corresponding cabling cost. In the measuring system, the participants in the communication are therefore wired to one another in order to establish the communication connection and/or a power supply. Along with the position sensors, further subsystems, for example probes, measuring heads, sensors, may also be present to record environmental conditions such as temperature, etc., or actuators such as axle drives, motorized tilt heads, display elements, etc., which similarly participate in the communication. In order to minimize the cabling costs, an attempt is made in the measuring machines to use as few communication connections as possible, preferably only one communication connection, for all subsystems involved. An attempt is also made to design the communication connections advantageously, i.e., for example, as far as possible to avoid duplicate line routing which, for example, occurs in a star-shaped cabling of each subsystem through to the controller.
Along with the subsystems described above, which are mainly permanently mounted on the measuring system, exchangeable components may also be involved in the measurement, for example exchangeable measuring heads, measuring probes, tilt heads, optical probe heads, etc., which are adapted to a wide variety of measuring tasks and are similarly incorporated into the communication. Since they may be exchanged during operation or in the event of a change of configuration of the machine, the communication system which is in operation may also be changed as a result. An exchange of a subsystem as a participant in the communication system may also be required in the event of service work and repairs.
In measuring systems of this type, the communication takes place between these devices or subsystems as the participants in the communication system, often via bus structures. For example, a bus structure, such as e.g. RS 232, RS422, RS423, RS485, or others, can be used for the communication. One conventional topology which is often advantageous in terms of the local arrangement of the participants in the measuring system is a serial structure. In the latter, the participants are disposed one after the other and are connected to the bus in each case with only one connection in each case between two subsystems. The participants often include a plurality of components of the same type, e.g. a plurality of position sensors of the same type, which communicate via the common bus with a control unit, i.e., for example, they forward the position information determined by them to the control unit. In the interests of a simple storage and maintenance, the subsystems of the same type are mainly without any difference prior to installation in the measuring system, so that they are usable at a wide variety of locations in the machine and in different machines.
However, it is important in the application to be able to distinguish and identify the subsystems connected to the bus, even if subsystems of the same type are involved. In the case of coordinate-measuring devices, it is essential, for example, during a measurement, to know which movement axis of the measuring system is being recorded with which position sensor.
For this purpose, for example, a communication address can be used which is settable in each case on the participants. This address is often only allocated immediately before or after the installation of the participant, e.g. by DIP switches, coding plugs, electronic programming devices, etc. However, a procedure of this type is prone to error and time-consuming.
A number of approaches for avoiding a manual address allocation can be found in the literature in other fields of technology. For example:
U.S. Pat. No. 5,666,557 describes an automatic addressing of peripheral devices in a data processing system using connector identifiers;
WO 98/03921 describes the automatic detection of the sequence of devices of a network communication device using a pulse length of an ancillary signal;
WO 2004/039010 describes a setting of addresses of child devices by a parent device;
WO 2007/104668 and DE 10 2006 025 174 describe an address allocation for driver assistance systems.
DE 10 2006 050 135, DE 10 2009 054 904 or DE 197 13 240 show address allocations in which, controlled by the control master, addresses are automatically allocated and the participants are assigned by reading out participant-specific information, i.e. similarly using participant-specific unique identifiers which are assigned exclusively to each of the participants.
A common feature of all these known approaches is that an address is allocated to the participants from outside. Even in the above approaches, this is still costly and in many cases requires additional hardware, such as coding switches, coding plugs, additional connector pins, etc., for this purpose. Similarly, the cost of allocating this address, whether it be in production, commissioning or during a bus initialization, is not negligible. An allocation of incorrect addresses is furthermore a frequent source of errors in measuring systems, especially when components are exchanged in the event of servicing. Not only malfunctions, but also hardware damage, can be caused by transposed addresses of communication participants.